The Clean Air Act Amendments of 1990 is a federal law that sets limits
on how much pollution is allowed in the air anywhere in the United
States. The goal is to make sure that all Americans have clean, healthy
air to breathe. EPA can fine violators who break the law and put too
much pollution into the air.

Parts of the Clean Air Act Amendments, called “Titles,” established
permit programs to limit the amount of pollutants that sources such
as factories, industries, and vehicles can release. These permits
are issued by states or EPA and include information on which pollutants
are being released, how much may be released, and what steps are being
taken to reduce the pollution. Sources of pollution have to pay for
the permits, and the money from the fees helps support state air pollution
control activities.

In addition, the Clean Air Act Amendments established a specific
program to reduce the pollutants that cause acid rain—sulfur
dioxide and nitrogen oxides. This program—the Acid Rain Program—uses
allowances to control the amount of pollution that a source can produce.
Each source can decide if it wants to buy, sell, or save these allowances.
There are stiff penalties, however, for sources that release more
pollutants than their allowances cover. As of 2001, the Acid Rain
Program had reduced sulfur dioxide emissions by 33 percent and nitrogen
oxide emissions by 27 percent. For more information, see the Plain
English Guide to the Clean Air Act.